The biology of bone grafting

Is open bone graft always necessary when treating aseptic subtrochanteric nonunion with a reamed intramedullary nail?

Background

This study aimed to compare the radiological results between closed nailing without bone graft (BG) and open nailing with BG for aseptic subtrochanteric nonunion and to determine when an open procedure with BG should be considered.

Methods

In this retrospective study, we investigated patients who underwent surgical intervention for subtrochanteric nonunion between January 2008 and March 2018 in two institutions. Patients with infection, large bone defect, pathologic fracture, open fracture, previous surgery using plate, and follow-up of less than 1 year were excluded. We compared the demographic details and radiological results between patients who underwent the open procedure with BG (BG group) and the closed procedure without BG (non-BG group) as a historical control, and risk factors for the failure of revision surgery were evaluated.

Results

Thirty-seven patients met the criteria and were divided into the following two groups: the BG group (n=19) who underwent open nailing with BG and the non-BG group (n=18) who underwent closed reamed nailing without BG. The mean degrees of correction of varus and flexion deformity were significantly different (p=0.001, respectively), 6.2° and 2.9° in the BG group and 4.1° and 0.6° in the non-BG group, respectively. Bony union was observed in 17 cases (89.5%) in an average of 7.4 months in the BG group and in 16 cases (88.9%) in 7.6 months in the non-BG group, with no significant differences. The factors that were significantly associated with failure of revision were atypical fracture, two or more previous surgeries, and varus and sagittal anterior angulation.

Conclusions

The radiological results of closed reamed nailing without BG for subtrochanteric nonunion were satisfactory. In the effort of percutaneous realignment, gap reduction, and intramedullary reaming, the radiological results of closed nailing without BG were not different from those of open nailing with BG; therefore, closed procedure without BG may be an acceptable option in appropriately selected patients.

Craniofacial Bone Grafting: Wolff's Law Revisited

Bone grafts are used for the reconstruction of congenital and acquired deformities of the facial skeleton and, as such, comprise a vital component of the craniofacial surgeon's armamentarium. A thorough understanding of bone graft physiology and the factors that affect graft behavior is therefore essential in developing a more intelligent use of bone grafts in clinical practice. This article presents a review of the basic physiology of bone grafting along with a survey of pertinent concepts and current research. The factors responsible for bone graft survival are emphasized.

The ingrowth of new bone tissue and initial mechanical properties of a degrading polymeric composite scaffold

Trabecular bone deficiency causes a dilemma at surgery in a variety of clinical situations, including trauma, tumor resection, and reconstruction. A synthetic material to replace trabecular bone would be biocompatible, provide temporary mechanical strength to the reconstructed region, and serve as a scaffold upon which new bone could grow (i.e., osteoconduction). In addition, it should serve as a carrier for osteoinductive biomolecules, degrade into nontoxic materials that the body can excrete via normal metabolic pathways, and allow the new bone to remodel along lines of local stress. A particulate filled composite based on an unsaturated linear polyester was designed as a candidate material for this application. The components are mixed with a monomer that cross links the double bonds of the unsaturated polyester. Degradation occurs via hydrolytic degradation of the backbone polymer's ester linkages. This strategy of prepolymer synthesis via condensation polymerization in the laboratory followed by cross linking the unsaturated prepolymer via radical polymerization at surgery offers design flexibility. The radical polymerization allows curing during surgery to facilitate reconstruction of various shaped defects. The laboratory synthesis of the prepolymer allows alterations of its composition and physical properties to effect desired properties in the resulting composite. This study investigates the effect of several composite material formulations on the in vitro mechanical properties and the associated in vivo histologic characteristics of the resulting material. The prepolymer molecular weight, presence of a leachable salt, and amount of cross linking monomer had strong effects on the resulting strength and modulus of the composite. These strengths were on the order of 5 MPa, a magnitude appropriate for consideration of the material as a temporary trabecular bone substitute. The in vivo studies in a rat proximal tibia model demonstrated progressive growth of new bone against the receding surface of the degrading material, and ingrowth of new bone trabeculae into the interior of the degrading specimen. The specimen was also well integrated with the surrounding bone, with no internal fibrosis. There was an absence of a foreign body inflammatory response to the presence of this material over a 5-week time span. This material may thus be an attractive candidate for temporary replacement of trabecular bone, facilitating both osteoconduction and osteoinduction.

Histological differences in iliac and tibial bone graft

BACKGROUND

Cancellous bone graft is frequently used during orthopedic procedures. While the iliac crest has traditionally been the most common donor site, the proximal tibia is an alternative donor site, especially for foot and ankle procedures. This study tested the null hypothesis that the histologic composition of iliac and tibial bone grafts is similar.

MATERIALS AND METHODS

Specimens from the iliac crest (n = 10) and tibia (n = 10) in excess of that needed for patients undergoing foot or ankle fusion were examined histologically. Iliac samples were taken from the anterior iliac crest. Tibial samples were harvested from the region of Gerdy's tubercle. Specimens were graded based on the percent of bone surfaces that opposed active hematopoietic marrow, with Grade I at 0%, through Grade VI at 81% to 100%. Differences between iliac and tibial grafts were evaluated with Fisher's Exact Test.

RESULTS

Iliac crest and tibial bone grafts both showed trabecular fragments with abundant osteocytes. All iliac grafts contained active hematopoietic marrow. In contrast, the medullary space of tibial grafts contained fat and little hematopoietic marrow. Nine iliac grafts were graded V or VI; whereas the ten tibial bone grafts were all graded I or II (p = 0.0001). The difference in the numbers of samples in each group ranked as grade VI was also statistically significant (p = 0.005).

CONCLUSION

Iliac bone grafts contained active hematopoietic marrow, whereas quiescent medullary fat predominated in tibial grafts.

CLINICAL RELEVANCE

These findings raise questions about the cellular contributions of different sources of bone graft to bone healing.

Effects of a new allograft processing procedure on graft healing in a canine model: a preliminary study

Graft healing in vivo can be affected by allograft processing. We asked whether a new processing technique influenced graft-host healing compared with autograft and a standard processing technique in a canine ulna model. We used bilateral intercalary allografts or autografts in the ulna of 13 skeletally mature male coonhounds. Each animal received two allografts, either one autograft and one allograft, or two autografts. At term (90 days), the graft sites were harvested. We assessed union with high-resolution xray imaging. Each specimen was processed for nondecalcified histologic analysis to assess the graft-host interface. Quantitative histomorphometric analysis was performed to determine spatial location and area of bone. Radiographic analysis, histologic analysis, and histomorphometric measures revealed no differences in union, mean total bone area, or total endosteal/intramedullary bone for the new process, standard process, and autografts. Our preliminary data suggest the new processing techniques may increase the safety of allograft transplantation without adversely affecting union when compared with standard processing techniques and autograft in a canine model.

[Voluminous bone graft harvesting of the femoral marrow cavity for autologous transplantation. An indication for the"Reamer-Irrigator-Aspirator-" (RIA-)technique]

Due to their excellent osteoinductive, osteogenetic, and osteoconductive properties, autologous bone grafts possess biomechanical advantages over synthetic bone substitutes. Furthermore, unlike cadaveric allografts and xenografts, they carry no risk of immunogenic response or transmission of infectious diseases. However, the limited availability of autologous bone grafts requires the use of the above-mentioned bone substitutes for management of large bone defects. The"Reamer-Irrigator-Aspirator-" (RIA-)technique may present an alternative method for harvesting a larger volume of autologous bone graft as compared with conventional harvesting procedures. We report on intramedullary reaming by the RIA technique to obtain autologous bone graft for a nonunion of the proximal femur. The contralateral femur was reamed and the bone graft was applied to the nonunion. The patient showed clinical and radiological healing of the nonunion without donor site complications.

Biomechanical analysis of tibial strength after harvest of unicortical tibial grafts from two different sites

BACKGROUND

Use of tibial strut grafts has several potential advantages over other donor sites and would be ideal as a harvest site for bone grafts if there are minimal or no resulting risks to tibial stability.

METHODS

Ten matched-pair cadaver tibiae were randomized to have a 1.5 x 4.0 cm cortical graft harvested from the tibial crest or 1 cm posterior to the tibial crest. Both locations were 6 cm distal to the tibial plateau. The grafts were removed using a high-speed oscillating saw, and each end of the tibia was mounted for testing and loaded onto a servohydraulic test frame. The samples were axially loaded with 720 N (162 lbs) of force, and an external rotational torque was applied at 5 degrees per second to failure. Failure torque for each tibia was recorded. A paired Student's t-test was used to determine whether any observed differences in failure torques were significant.

RESULTS

The torque to failure range for on-crest grafts was 11.65 to 81.76 Nm (average, 44.53 Nm; SD, 22.82 Nm). The torque to failure range for the tibiae with the graft 1 cm off-crest was 13.30 to 70.45 Nm (average, 41.64 Nm; SD, 17.83 Nm). All fractures were spiral, included the distalmost anterior corner of the donor site, and extended distally. There was no significant difference in torque to failure between the two donor sites (p = 0.22). The grafts varied consistently in quality.

CONCLUSION

Considering that there was no statistically significant difference in torque to failure between the two groups of tibiae, the site for tibial bone graft can be selected based on the shape of the cortical graft necessary for each specific surgery.

Management of bony deficiency in revision anterior cruciate ligament reconstruction using allograft bone dowels: surgical technique

Revision anterior cruciate ligament (ACL) reconstruction surgery has become increasingly common over the past decade and its popularity is likely to rise further as the number of primary ACL reconstructions increases each year. More than 75% of all cases of failed ACL reconstruction are the result of technical error and, of these, more than 70% are attributed specifically to malpositioned tunnels. Management of tunnel malposition in revision surgery often requires innovative approaches for dealing with the resultant bony defects. In addition, tunnel osteolysis may create bone loss that interferes with desired tunnel placement. A number of options have been described for handling these bony deficiencies, many of which are technically difficult and time consuming. We describe a novel technique to address bony defects during revision ACL reconstruction using freeze-dried allograft bone dowels. These allografts are readily available and can be used easily to fill deficiencies resulting from previous tunnels or osteolysis. The grafts provide sufficient structural support for redrilling of new tunnels through or next to the bony plug, allowing uncompromised tunnel placement.

Anterior iliac crest bone graft harvesting using the corticocancellous reamer system

OBJECTIVE

To evaluate the anterior iliac crest bone graft harvesting procedure using a corticocancellous acetabular reamer system.

DESIGN

A total of 390 bone grafting procedures were reviewed using retrospective chart review. Two hundred twenty procedures were performed using the reamer system, and 170 were performed using traditional techniques (cortical strip, tricortical wedge, and cancellous trap door grafts).

SETTING

The Hospital for Special Surgery, New York, New York.

PARTICIPANTS

Operative cases involving an anterior iliac crest bone graft procedure between January 1, 1991 and February 28, 1998.

MAIN OUTCOME MEASUREMENTS

Complications were organized by the categories major, intermediate, and minor. Statistical analysis included assessment of comorbidity to determine risk factors that may be associated with a propensity for complications.

RESULTS

Of the 390 patients reviewed, 13.1 percent (51 of 390) developed a total of seventy-one complications. Of the seventy-one complications, forty were reamer-associated and thirty-one were traditional method-associated complications. As compared with the traditional group, major morbidity was lower in the reamer group (0.9 percent [2 of 220] as compared with 1.8 percent [3 of 170] [ p = 0.4]). Intermediate and minor morbidity were slightly higher in the reamer group than in the traditional group (5.9 percent [13 of 220] as compared with 5.3 percent [9 of 170] [ p = 0.7] and 9.5 percent [21 of 220] as compared with 7.1 percent [12 of 170] [ p = 0.4], respectively). Of the forty reamer-associated complications, 90 percent (36 of 40) resolved within ninety days (average 36.6 days). Of the thirty-one traditional method-associated complications, 74.2 percent (23 of 31) were resolved by 90 days (average 50.6 days). Using logistical regression analysis obesity (body mass index) ( p = 0.03) and smoking ( p = 0.03) were correlated with development of a complication. Furthermore, if a patient was obese and a smoker, the analysis predicted an 83 percent chance of developing a complication.

CONCLUSIONS

The reamer technique was found to be safe and efficacious while producing a large amount of autogenous corticocancellous bone graft. Overall complication rates for the reamer and the traditional groups were comparable. The corticocancellous reamer system represents an effective option for bone graft harvesting.

Treatment of femoral shaft aseptic nonunions: comparison between closed and open bone-grafting techniques

OBJECTIVE

The aim of this prospective study was to investigate and compare the effects of closed and open bone-grafting techniques in the treatment of femoral shaft aseptic nonunions.

MATERIALS AND METHODS

Forty consecutive femoral shaft aseptic nonunions with inserted reamed intramedullary nails were randomly divided into two groups. The indications for these techniques were aseptic nonunions with less than 1 cm of shortening, no rotational or angular misalignment, and no large bony defects. The closed technique consisted of intramedullary reaming to a larger size and reinsertion of a stable intramedullary nail. The open technique consisted of local debridement, maintaining local stability with or without supplementation, and upper tibial cancellous bone grafting.

RESULTS

Thirty-five cases were followed up for at least 1 year (range, 1-3 years), and all achieved solid unions. There were no significant complications. The union period with the closed technique was significantly shorter than with the open technique (4.0 +/- 0.6 months vs. 5.1 +/- 0.8 months; p < 0.01, Student's t test). The operating time with the closed technique was also significantly shorter than with the open technique (36 +/- 7 minutes vs. 58 +/- 14 minutes; p < 0.01, Student's t test). There was no significant difference in other parameters between the two techniques.

CONCLUSIONS

The closed bone-grafting technique had clinical results similar to those of the open technique. The surgical procedure was simpler, however, and the union period was shorter. Whenever possible, therefore, the closed technique should be considered in all indicated cases.

Complications of iliac crest bone graft harvesting

Autologous bone grafts harvested from the iliac crest are commonly used in reconstructive orthopaedic surgery. Autologous bone is used to help promote bone healing in fractures and to provide structural support for reconstructive surgery. The results of autologous bone grafting are more predictable than the use of xenografts, cadaveric allografts, or synthetic bone substitutes because autologous bone grafts provide osteoinductive and osteoconductive properties, are not immunogenic, and are usually well incorporated into the graft site. In a retrospective review of 414 consecutive cases of iliac crest bone graft procedures performed at Brooke Army Medical Center from 1983 to 1993, 41 (10%) minor and 24 (5.8%) major complications were identified. Minor complications included superficial infections, superficial seromas, and minor hematomas. Major complications included herniation of abdominal contents through massive bone graft donor sites, vascular injuries, deep infections at the donor site, neurologic injuries, deep hematoma formation requiring surgical intervention, and iliac wing fractures. Harvesting of iliac crest bone graft can be associated with significant morbidity. However, with adequate preoperative planning and proper surgical technique, the incidence of these complications can be reduced.

Preliminary experience with a novel model assessing in vivo mechanical strength of bone grafts and substitute materials

A novel canine tibia model was used to evaluate four bone graft materials: autologous cortical bone, allograft cortical bone, hydroxyapatite/tricalcium phosphate (HA/TCP) ceramic granules, and a HA/TCP and collagen composite. Mechanical material properties were assessed using custom-designed stainless steel plugs for control of graft volume and interface surface area. These plugs held the bone graft materials in the cortex of the tibia shaft and allowed in vivo mechanical testing. After 6 months of ad lib weight bearing, the grafts were harvested and tested in torsion. The samples in each animal were compared with the test plugs into which new bone had grown without the addition of graft. Control bone peak shear strength averaged 47 (+/- 8.3) MPa (6.78 +/- 1.2 kpsi). Compared on the basis of peak torque, stiffness, and energy to peak torque, no significant differences were found among any of the graft materials or control bone. Histologic examination revealed the materials to be osteoconductive with the extensive formation of dense, compact cancellous bone. The new bone in the autograft and allograft samples completely filled the available space, whereas gaps persisted in the synthetic ceramics.